1. Field of the Invention
The present invention relates to metal oxide.organopolysiloxane hybrid particles, and a powder composition made from those particles, and a method for the preparation thereof, and still further relates to a cosmetic composition in which said metal oxide organopolysiloxane hybrid particles are blended.
2. Description of the Prior Art
The powder of titanium oxide, which is well-known to have high refractive index among metal oxides is broadly used as the white pigment, because of it's excellent hiding power and is chemically stabilized. However, this high refractive index sometimes can become a weak point. Especially, when it is applied in a cosmetic composition, it becomes a ground to cause unnatural makeup, which is so called as “an excessively pale-white look”. Therefore, when a metal oxide having high refractive index e.g. titanium oxide is used in a cosmetic composition, various countermeasures to avoid said serious problem are taken, for example, altering the shape or particle size of the powder or forming a complex with other materials. However, since the refractive index is the essential feature of each powder, above mentioned countermeasures are not sufficient to dissolve said serious problem.
Further, some metal oxides have a tendency to cause cohesion in medium, and powder of these metal oxides are difficult to maintain stable dispersion state. Still further, since the powder of metal oxide is easily wetted by water, a coated film of blended product in which these mentioned powders are blended have a defect of weak resistance to water. For the purpose to dissolve these problems, the method to provide water repellency by treating the surface of powder with a surface treatment agent such as organopolysiloxane or fluorine type high molecular compound. However, although it is possible to provide water repellency and to improve water resistance by said method, the improvement of dispersing ability and dispersing stability are not sufficient.
In the meanwhile, porous inorganic powder represented by silica gel is widely used as an absorbing agent, as an impregnating agent or as a carrier of catalyst based on it's large specific surface area. And in the field of materials for cosmetic composition, the porous powder is used in various forms. Mainly, the porous inorganic powder is blended in a cosmetic compound for the purpose to obtain long-lasting of makeup by removing sebum or sweat, or to provide light and smooth feeling.
A hybrid material composed of metal oxide and organic compound have been developed and a powder of hybrid material prepared by covalent bond of metal oxide and organic high molecular compound is proposed (JP7-265686A). Typically, the powder of the proposed invention can be obtained by following method. A seed particle, which is high molecular compound, obtained by polymerizing vinyl type monomer, is swelled by a swelling solvent containing polymerable metal alkoxide possessing vinyl group. After that, said polymerable metal alkoxide is polymerized. Then, the hybrid of the present invention can be obtained by carrying out hydrolysis and condensation reaction. The proposed invention is characterized by particles having uniform particle size.